Method and apparatus for noise filtering

a technology of noise filtering and noise filtering chamber, which is applied in the direction of transducer casing/cabinet/support, electrical transducer, instruments, etc., can solve the problems of communication problems in noisy environments such as in offices and modes of transportation

Inactive Publication Date: 2005-10-04
SIEMENS CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the field of sound, noisy environments such as in modes of transport and offices present a communications problem, particularly when one is attempting to carry on a phone conversation.

Method used

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  • Method and apparatus for noise filtering
  • Method and apparatus for noise filtering

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Embodiment Construction

[0031]This invention generalizes the minimum variance estimators of Y. Ephraim and D. Malah, supra, to a two-channel scheme, by making use of a second microphone signal to further enhance the useful target signal at reduced level of artifacts.

[0032]Referring to FIG. 1, a pair of signals, x1 and X2 are input from a pair of microphones 10 and each signal is received separately through a pair of channels 15a, 15b into separate discrete Fourier transformers 20 to yield Fourier transformed signals X1 and X2. The microphones may be spaced any suitable distance apart, and will typically be spaced within a fraction of an inch apart when the invention is used on small devices, such as cellphones, but may be spaced many feet apart for use in conference rooms or other large spaces. The invention may be used indoors or outdoors.

[0033]A mixing model may be given by:

x1(t)=s(t)+n1(t)  (1)

x2(t)=k*s(t)+n2(t)  (2)

where x1(t), x2(t) are the two synchronously sampled signals, s(t) is the target signal ...

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Abstract

Disclosed is an apparatus for and a method of filtering noise from a mixed sound signal to obtained a filtered target signal, comprising the steps of inputting the mixed signal through a pair of microphones into a first channel and a second channel, separately Fourier transforming each said mixed signal into the frequency domain, computing a signal short-time spectral amplitude |Ŝ| from said transformed signals, computing a signal short-time spectral complex exponential ei arg(S) from said transformed signals, where arg(S) is the phase of the target signal in the frequency domain, computing said target signal S in the frequency domain from said spectral amplitude and said complex exponential.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims priority to U.S. Provisional Patent Application Ser. No. 60 / 326,626, filed Oct. 2, 2001, which is hereby incorporated by reference.FIELD OF THE INVENTION[0002]This invention relates to filtering out target signals from background noise.BACKGROUND OF THE INVENTION[0003]There has always been a need to separate out target signals from background noise, whether the signals in question are sound or electromagnetic radiation. In the field of sound, noisy environments such as in modes of transport and offices present a communications problem, particularly when one is attempting to carry on a phone conversation. One known approach to this problem is a two-microphone system, wherein two microphones are placed at fixed locations within the room or vehicle and are connected to a signal processing device. The speaker is assumed to be static during the entire use of this device. The goal is to enhance the target signal by...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G10L19/00G10L19/14H04B15/00G10L21/02
CPCG10L21/0208H04R3/005
Inventor BALAN, RADU VICTORROSCA, JUSTINIAN
Owner SIEMENS CORP
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